In recent years, for transmission apparatuses, due to increase in traffic through the Internet, and the like, increase in data capacity, reduction in size of devices, and cost reduction are desired to be achieved. In order to achieve increase in data capacity, reduction in size of devices, and cost reduction, a wide variety of optical pluggable modules (which will be hereinafter referred to as modules) in accordance with a transmission distance and a status of support for an internal function, or the like, have been developed. A transmission apparatus is configured such that a predetermined module is mounted on each line card in the apparatus, and thus, corresponds to a desired specification. Interfaces of various different transmission rates are used for the modules, and data transmission is realized in the line cards via the interfaces.
FIG. 11 and FIG. 12 are block diagrams illustrating related art examples of a line card. As illustrated in FIG. 11, a line card 600 includes a CFP module 601 (CFP: 100 G form-factor pluggable, the c stands for the Latin letter used for expressing the number of 100), a framer 602, an electrical interface 603, a card controller 604, and a connection connector 605. The line card 600 has a transmission capacity corresponding to 100 Gbps×2 ports, which is realized by the two CFP modules 601. A signal externally input in each of the CFP module 601 is processed in the corresponding framer 602 via the corresponding electrical interface 603. In this case, the electrical interface 603 has a configuration of 11.18 Gbps×10 lanes at a rate of OUT-4 (optical transport unit 4).
As illustrated in FIG. 12, a line card 700 includes a CFP2 module 701, a framer 702, a gear box 703, an electrical interface 704, an electrical interface 705, a card controller 706, and a connection connector 707. Similar to the line card 600, the line card 700 has a transmission capacity corresponding to 100 Gbps×2 ports, which is realized by the two CFP2 modules 701. In the line card 700, the gear box 703 configured to change 28 Gbps×4 lanes to 11.18 Gbps×10 lanes is provided between each of the CFP2 module 701 and the corresponding framer 702. A signal externally input in the CFP2 module 701 is input to the corresponding gear box 703 via the electrical interface 704 of 28 Gbps×4 lanes, and then, is transmitted from the gear box 703 to the framer 702 via the corresponding electrical interface 705 of 11.18 Gbps×10 lanes.
In the electrical interface 603 of the line card 600 and the electrical interfaces 704 and 705 of the line card 700, in order not to cause bit error generation, characteristic optimization for a transmission device (for example, the CFP module 601 in the line card 600, or the like) and a reception device (for example, the framer 602 in the line card 600 or the like) is performed. In the characteristic optimization, the characteristic of the transmission device, the characteristic of the reception device, and the characteristic of a transmission channel between the transmission device and the reception device are modeled, and setting values for the transmission device and the reception device are determined by simulation using the model, or the like. For example, examples of a setting value for the transmission device include an amplitude value of a transmission output, a pre/post-emphasis value, and the like. Examples of a setting value for the reception device include an equalizer gain value, and the like.
Validity of a setting value for the transmission device and a setting value for the reception device, which have been derived by the above-described simulation, is checked by real machine verification in which the setting values are actually set to the transmission device and the reception device and an error rate is checked, or the like. After the validity is confirmed, the setting values are set to the line cards 600 and 700 and thus an operation is performed, so that the generation of a bit error is not caused in the line cards 600 and 700, and stable signal transmission is realized.
Japanese Laid-open Patent Publication No. 2010-34777 discusses a related art example.
Incidentally, the characteristic of a transmission channel between the transmission device and the reception device changes due to an external (surrounding) environment, such as a temperature and a humidity on the transmission channel. FIG. 13 is a chart illustrating the characteristic of a transmission channel. In FIG. 13, the ordinate axis indicates the magnitude (MAGNITUDE) of a transmission channel loss. The abscissa axis indicates a frequency (FREQUENCY) at transmission and also a transmission speed (a transmission rate) on the transmission channel. Graphs G1 and G2 indicate the characteristic of the transmission channel (the transmission speed−the transmission channel loss) in different external environments.
As illustrated in FIG. 13, values at frequencies F1 and F2 differ between the graphs G1 and G2 and, when the external environment differs, the characteristic of the transmission channel changes. As the transmission speed increases (the frequency F1 to the frequency F2), the transmission channel loss greatly increases, so that the change in characteristic of the transmission channel due to the change in external environment increases.